The present invention relates to sidelobe jammer cancellation systems, and more particularly to such a system for radar and communication systems which require wideband signals.
Conventional adaptive sidelobe cancellers are narrow band and narrow angle because the mismatch of amplitude and phase between the auxiliary antenna and the main antenna restricts the cancellation bandwidth and angle.
Multiple auxiliary antennas have been previously proposed to handle a wideband jammer, but were relatively costly and complex. Robert A. Shore and Ronald L. Fante, "Sector Sidelobe Nulling," RADC-TR-81-326, Rome Air Development Center report, November 1981.
Cancellation systems using multiple tapped delay lines and adaptive weights have also been proposed for wideband nulling. J. H. Chang and F. B. Tuteur, "A New Class of Adaptive Array Processors," J. Acoust. Soc. Am., Vol. 49, No. 3, March 1971, pages 639-649; W. E. Rodgers and R. T. Compton, Jr., "Adaptive Array Bandwidth with Tapped Delay-line Processing," IEEE Trans. Aerospace Electronic Systems, Vol. 1, AES-15, No. 1, January 1979, pages 21-28. The costs of multiple weights and time delay lines, and the control of all weights make such systems impractical for wideband radar and communication systems.
It is therefore an object of this invention to provide a wideband, wide angle jammer cancellation system for such applications as imaging radars and frequency hopping or pseudo random noise coded communication systems, and which does not require multiple auxiliary antennas or multiple tapped delay lines and weights for wideband cancellation.
A further object of the invention is to provide a jammer cancellation system employing an auxiliary array, wherein good phase and amplitude matching is achieved between the main array and the auxiliary array, and wherein the auxiliary array has a null at the main beam direction so that gain degradation of the desired signal does not occur.